July 16, 2008

A colony that contains nearly half of the black-footed ferrets in the United States and that biologists say is critical to the long- term health of the species has been struck by plague, which may have killed a third of the 300 animals.

A much-publicized endangered species in the 1970s that had dwindled to 18 animals, the black-footed ferret had struggled to make a comeback and had been doing relatively well for decades. But plague, always a threat to the ferrets and their main prey, prairie dogs, has struck with a vengeance this year, partly because of the wet spring.

The ferrets are an easy target for the bacteria.

"They are exquisitely sensitive to the plague," said Travis Livieri, a wildlife biologist who is trying to save the colony. "They don't just get sick, they die. No ifs, ands or buts."

Humans can catch plague, but it is easily treated with antibiotics.

Livieri is working with the U.S. Fish and Wildlife Service black- footed ferret recovery team, the Forest Service and volunteers to try to save the colony at Conata Basin - a buffer strip of federal land adjacent to private grazing land - by dusting prairie dog burrows with flea powder that kills the plague-carrying insects. Livieri is also working on a vaccination program, prowling the prairie all night to capture ferrets for injections.

But the fight is not only against the plague.

While the U.S. Forest Service is part of the effort to protect ferrets, it has also, at the request of area ranchers, poisoned several thousand acres infested with prairie dogs on the edge of the Conata Basin. The buffer strip does not have ferrets, but it is good ferret habitat, experts say, and if they were to spread there, it could help support the recovery.

But prairie dogs eat grass, and a large village can denude grazing land. The rodent, in fact, has long been detested in the West as a pest.

Of even more concern to biologists and environmentalists, though, is a Forest Service study of an expanded effort to kill prairie dogs in ferret habitat, which biologists say could be devastating to the restoration of the ferrets.

J. Michael Lockhart, the former director of the recovery effort for the Fish and Wildlife Service, retired in January in part to protest the poisoning of prairie dogs, believing that could jeopardize the fragile gains of the ferret. "I think it's insane," said Lockhart, now a wildlife consultant. "Those sites are so important. They need to preserve as much of that habitat as they can."

A decision by the Forest Service on whether to poison prairie dogs on land that has no ferrets, but is suitable habitat for them, is due out soon. A decision on whether to poison prairie dogs in ferret habitat is being delayed, said the under secretary of agriculture, Mark Rey, to see how the spread of the plague plays out. "We'll see how big it is, how far it is likely to spread and how many prairie dogs we have left as it runs its course," Rey said. "Prudence dictates we collect this information."

But Rey said that to not deal with prairie dogs could hurt the program. "Prairie dogs are spreading off federal land to private land," he said. "And our goal is to keep the black-footed ferret program with broad public support, and one way to do that is to make sure prairie dogs don't spread onto private land."

Black-tailed prairie dogs, food for numerous prairie predators, may be threatened themselves. A few years ago the Fish and Wildlife Service, in response to a petition, decided they were warranted for listing as a protected species, but precluded because of higher priorities. That designation was later changed and is now being reconsidered.

For now, though, efforts are focused on stopping the disease.

Losing this population to the plague would be a blow for the entire ferret recovery program and personally heartbreaking, said Livieri, who has worked for 13 years to restore this population south of Badlands National Park. He started with the National Park Service, then worked for the Forest Service and now cobbles together financing for his own nonprofit organization, Prairie Wildlife Research.

Until now this was the most robust population of ferrets, so healthy it provided wild kits for other recovery efforts in Colorado, Montana, Utah, Mexico and elsewhere. "Last year, 52 ferrets came out of here to supplement or start new populations," Livieri said.

Most of those populations have struggled with plague and other problems. One population, near Shirley Basin, Wyoming, has struggled with plague but now may have close to the number of ferrets here. There are thought to be about 1,300 ferrets extant - 1,000 or so in the wild and 300 in captivity.

Plague thrives in wet years, and this has been one of the wettest in the region in years. A combination of insecticide and vaccines can be very effective, said Dean Biggins, a research biologist with the U.S. Geological Survey, who has studied plague and ferrets. He said he had seen a plague outbreak hit a line of dusted burrows and stop cold. "There's no question they can be protected," he said.

"It's not whether we can do it, but are we willing because of cost and labor? It might have to be done every year or two."

For now, the race is on to protect the heart of the ferret population. Livieri, often working by himself, drives from his home in Wellington, Colorado, six hours away, and spends a week or two at a time scouring the prairie all night in hopes of injecting all of the ferrets.

Treating ferrets, though, is only half of the equation. Enough prairie dogs need to survive the plague to keep the ferrets from starving to death. One ferret eats 125 to 150 prairie dogs a year.